How is chronic hypertension during pregnancy defined?

Answer

Chronic hypertension is defined as blood pressure exceeding 140/90 mm Hg before pregnancy or before 20 weeks' gestation. When hypertension is first identified during a woman's pregnancy and she is at less than 20 weeks' gestation, blood pressure elevations usually represent chronic hypertension.

In contrast, new onset of elevated blood pressure readings after 20 weeks' gestation mandates the consideration and exclusion of preeclampsia. Preeclampsia occurs in 3-6% of all pregnancies and the incidence is 1.5 to 2 times higher in first time pregnancies.
[7] Hypertensive disorders in pregnancy may cause maternal and fetal morbidity, and they remain a leading source of maternal mortality.

The following is a computed tomography (CT) image of the brain in woman who suffered an eclamptic seizure.

Nonenhanced computed tomography scan of a woman's brain following an eclamptic seizure, showing hypodense areas involving white matter of the occipital lobes and the high frontal/parietal lobes. Courtesy of Aashit K Shah, MD.

Noncardiogenic pulmonary edema in a patient with preeclampsia. This is due to a capillary leak that can be a primary component of preeclampsia. The radiograph demonstrates a diffuse increase in lung markings without the cephalization or vascular redistribution that is seen in patients with pulmonary edema from systolic dysfunction. This patient had rapid clinical improvement after only 10 mg of intravenous furosemide.